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*Chemistry Extern > 6.4 Creatinine, Uric Acid, BUN, and Ammonia > Flashcards

6.4 Creatinine, Uric Acid, BUN, and Ammonia Flashcards

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1
Q

Creatinine is formed from the:
A. Oxidation of creatine
B. Oxidation of protein
C. Deamination of dibasic amino acids
D. Metabolism of purines

A

A. Oxidation of creatine

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2
Q

Creatinine is considered one of the substances of choice to measure endogenous renal clearance because:
A. The rate of formation per day is independent of body size
B. It is completely filtered by the glomeruli
C. Plasma levels are highly dependent upon diet
D. Clearance is the same for both men and women

A

B. It is completely filtered by the glomeruli

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3
Q

Which statement regarding creatinine is true?
A. Serum levels are elevated in early renal disease
B. High serum levels result from reduced glomerular filtration
C. Serum creatine has the same diagnostic utility as serum creatinine
D. Serum creatinine is a more sensitive measure of renal function than creatinine clearance

A

B. High serum levels result from reduced glomerular filtration

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4
Q

Which of the following formulas is the correct expression for creatinine clearance?
A. Creatinine clearance = U/P × V × 1.73/A
B. Creatinine clearance = P/V × U × A/1.73
C. Creatinine clearance = P/V × U × 1.73/A
D. Creatinine clearance = U/V × P × 1.73/A

A

A. Creatinine clearance = U/P × V × 1.73/A

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5
Q

Which of the following conditions is most likely to cause a falsely high creatinine clearance result?
A. The patient uses the midstream voiding procedure when collecting his or her urine
B. The patient adds tap water to the urine container because he or she forgets to save one of the urine samples
C. The patient does not empty his or her bladder at the conclusion of the test
D. The patient empties his or her bladder at the start of the test and adds the urine to the collection

A

D. The patient empties his or her bladder at the start of the test and adds the urine to the collection

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6
Q

The modification of diet in renal disease (MDRD) formula for calculating estimated glomerular filtration rate (eGFR) requires which four parameters?
A. Urine creatinine, serum creatinine, height, weight
B. Serum creatinine, age, gender, race
C. Serum creatinine, height, weight, age
D. Urine creatinine, gender, weight, age

A

B. Serum creatinine, age, gender, race

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7
Q

What substance may be measured as an alternative to creatinine for evaluating GFR?
A. Plasma urea
B. Cystatin C
C. Uric acid
D. Potassium

A

B. Cystatin C

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8
Q

Which of the following enzymes allows creatinine to be measured by coupling to a peroxidase reaction?
A. Glucose-6-phosphate dehydrogenase
B. Creatinine deaminase
C. Sarcosine oxidase
D. Creatine kinase (CK)

A

C. Sarcosine oxidase

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9
Q

Select the primary reagent used in the Jaffe method for creatinine.
A. Alkaline copper II sulfate
B. Saturated picric acid and sodium hydroxide (NaOH)
C. Sodium nitroprusside and phenol
D. Phosphotungstic acid

A

B. Saturated picric acid and sodium hydroxide (NaOH)

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10
Q

Interference from other reducing substances can be partially eliminated in the Jaffe reaction by:
A. Measuring the product at 340 nm
B. Measuring the product with an electrode
C. Measuring the timed rate of product formation
D. Performing a sample blank

A

C. Measuring the timed rate of product formation

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11
Q

Which of the following statements is true?
A. Cystatin C is measured immunochemically
B. The calibrator used for cystatin C is traceable to the National Bureau of Standards calibrator
C. Cystatin C assays have a lower coefficient of variation compared with plasma creatinine
D. Enzymatic and rate Jaffe reactions for creatinine give comparable results

A

A. Cystatin C is measured immunochemically

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12
Q

In which case would eGFR derived from the plasma creatinine likely give a more accurate measurement of GFR compared with measurement of plasma cystatin C?
A. Diabetes
B. Chronic renal failure
C. After renal transplantation
D. Chronic hepatitis

A

C. After renal transplantation

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13
Q

A sample of amniotic fluid collected for fetal lung maturity studies from a woman whose pregnancy was compromised by hemolytic disease of the fetus and newborn (HDFN) has a creatinine level of 88 mg/dL. What is the most likely cause of this result?
A. The specimen is contaminated by blood
B. Bilirubin has interfered with the measurement of creatinine
C. A random error occurred when the absorbance signal was being processed by the analyzer
D. The fluid is urine from accidental puncture of the urinary bladder

A

D. The fluid is urine from accidental puncture of the urinary bladder

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14
Q

Which analyte should be reported as a ratio using creatinine concentration as a reference?
A. Urinary microalbumin
B. Urinary estriol
C. Urinary sodium
D. Urinary urea

A

A. Urinary microalbumin

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15
Q

Urea is produced from:
A. The catabolism of proteins and amino acids
B. Oxidation of purines
C. Oxidation of pyrimidines
D. The breakdown of complex carbohydrates

A

A. The catabolism of proteins and amino acids

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16
Q

Urea concentration is calculated from the BUN by multiplying by a factor of:
A. 0.5
B. 2.14
C. 6.45
D. 14

A

B. 2.14

17
Q

Which of the statements below about serum urea is true?
A. The levels are independent of diet
B. Urea is not reabsorbed by the renal tubules
C. High BUN levels can result from necrotic liver disease
D. BUN is elevated in prerenal as well as renal failure

A

D. BUN is elevated in prerenal as well as renal failure

18
Q

A patient’s BUN is 60 mg/dL and serum creatinine is 3.0 mg/dL. These results suggest:
A. Laboratory error measuring BUN
B. Renal failure
C. Prerenal failure
D. Patient was not fasting

A

C. Prerenal failure

19
Q

Urinary urea measurements may be used for calculation of:
A. Glomerular filtration
B. Renal blood flow
C. Nitrogen balance
D. All of these options

A

C. Nitrogen balance

20
Q

BUN is determined electrochemically by coupling the urease reaction to the measurement of:
A. H2O2
B. The timed rate of increase in conductivity
C. The oxidation of ammonia
D. CO2

A

B. The timed rate of increase in conductivity

21
Q

In the ultraviolet enzymatic method for BUN, the urease reaction is coupled to a second enzymatic reaction using:
A. Aspartate aminotransferase (AST)
B. Glutamate dehydrogenase (GLD)
C. Glutamine synthetase
D. Alanine aminotransferase (ALT)

A

B. Glutamate dehydrogenase (GLD)

22
Q

Which product is measured in the coupling step of the urease-UV method for BUN?
A. CO2
B. Dinitrophenylhydrazine
C. Diphenylcarbazone
D. NAD+

A

D. NAD+

23
Q

Which enzyme deficiency is responsible for phenylketonuria (PKU)?
A. Phenylalanine hydroxylase
B. Tyrosine transaminase
C. p-Hydroxyphenylpyruvic acid oxidase
D. Homogentisic acid oxidase

A

A. Phenylalanine hydroxylase

24
Q

Which of the following conditions is classified as a renal-type aminoaciduria?
A. Fanconi syndrome
B. Wilson disease
C. Hepatitis
D. Homocystinuria

A

A. Fanconi syndrome

25
Q

Which aminoaciduria results in the overflow of branched chain amino acids?
A. Hartnup disease
B. Alkaptonuria
C. Homocystinuria
D. Maple syrup urine disease

A

D. Maple syrup urine disease

26
Q

In addition to phenylketonuria, maple syrup urine disease, and homocystinuria, what other aminoaciduria can be detected by MS/MS?
A. Alkaptonuria
B. Hartnup disease
C. Citrullinemia
D. Cystinuria

A

C. Citrullinemia

27
Q

Of the methods used to measure amino acids, which is capable of measuring fatty acids simultaneously?
A. MS/MS
B. HPLC
C. Capillary electrophoresis
D. Two-dimensional TLC

A

A. MS/MS

28
Q

Blood ammonia levels are usually measured to evaluate:
A. Renal failure
B. Acid–base status
C. Hepatic coma
D. GI malabsorption

A

C. Hepatic coma

29
Q

Enzymatic measurement of ammonia requires which of the following substrates and coenzymes?
A. 2-oxogluterate/NADH
B. Glutamate/NADH
C. Glutamine/ATP
D. Glutamine/NAD+

A

A. 2-oxogluterate/NADH

30
Q

Which statement about ammonia is true?
A. Normally, most of the plasma ammonia is derived from peripheral blood deamination of amino acids
B. Ammonia-induced coma can result from salicylate poisoning
C. Hepatic coma can result from Reye syndrome
D. High plasma ammonia is usually caused by respiratory alkalosis

A

C. Hepatic coma can result from Reye syndrome

31
Q

SITUATION: A sample for ammonia assay is taken from an IV line that had been capped and injected with lithium heparin (called a heparin lock). The sample is drawn in a syringe containing lithium heparin and immediately capped and iced. The plasma
is separated and analyzed within 20 minutes of collection, and the result is 50 µg/dL higher than one measured 4 hours before. What is the most likely explanation of these results?
A. Significantly greater physiological variation is seen with patients with systemic, hepatic, and GI diseases
B. The syringe was contaminated with ammonia
C. One of the two samples was collected from the wrong patient
D. Stasis of blood in the line caused increased ammonia

A

D. Stasis of blood in the line caused increased ammonia

32
Q

Uric acid is derived from:
A. Oxidation of proteins
B. Catabolism of purines
C. Oxidation of pyrimidines
D. Reduction of catecholamines

A

B. Catabolism of purines

33
Q

Which of the following conditions is associated with hyperuricemia?
A. Renal failure
B. Chronic liver disease
C. Xanthine oxidase deficiency
D. Paget disease of the bone

A

A. Renal failure

34
Q

Orders for uric acid are legitimate stat requests because:
A. Levels above 10 mg/dL cause urinary tract calculi
B. Uric acid is hepatotoxic
C. High levels induce aplastic anemia
D. High levels cause joint pain

A

A. Levels above 10 mg/dL cause urinary tract calculi

35
Q

Which uric acid method is associated with negative bias caused by reducing agents?
A. Uricase coupled to the Trinder reaction
B. UV uricase reaction coupled to catalase and alcohol dehydrogenase (ADH) reactions
C. Measurement of the rate of absorbance decrease at 290 nm after addition of uricase
D. Amperometry

A

A. Uricase coupled to the Trinder reaction

*Chemistry Extern (18 decks)

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